This invention relates to an internal combustion engine with an exhaust gas recirculation system, more especially, to an internal combustion engine with an exhaust gas recirculation system which engine is provided with a specially-designed fuel preparation device.
Well known are exhaust gas recirculation engines which recirculate a part of the exhaust gas extracted from an exhaust system of the engine into an intake system of the engine of reducing harmful contaminants, especially nitrogen oxides (NO.sub.x), contained in the exhaust gas. In these engines, the exhaust system and the intake system of the engine are communicated with each other via an exhaust gas recirculation control valve so that a part of the exhaust gas in the exhaust system is recirculated into the intake system in accordance with a predetermined program.
Many of the carburetors installed in the above-described well-known exhaust gas recirculation engines comprise a primary system and a secondary system. The entrance of such a carburetor is communicated with an intake air supply and the exit of the carburetor is communicated with a plurality of combustion chambers of the engine via an intake passage. The intake passage comprises an entrance portion connected to the exit of the carburetor and a plurality of exit portions which are branched from a branch portion of the intake passage and which communicate the entrance portion with the combustion chambers, respectively. An exhaust gas supply pipe is disposed on the wall of the intake passage at a position between the entrance portion and the branch portion and communicated with an exhaust gas recirculation control valve so that a part of the exhaust gas emitted from the combustion chambers is recirculated into the intake passage through the exhaust gas supply pipe.
The above-described conventional exhaust gas recirculation engine may cause a defect wherein the exhaust gas recirculation ratio, which is defined by a percentage of the weight of the recirculated exhaust gas to that of the intake air and normally called the "EGR ratio", becomes uneven between the combustion chambers, i.e., cylinders of the engine. As a result of the unevenness of the EGR ratio, when the amount of the recirculated exhaust gas is increased, some of the combustion chambers are supplied with more exhaust gas than other combustion chambers, and then a misfire due to the excessive exhaust gas is caused in those combustion chambers containing such excessive amounts of exhaust gas. As a result, amounts of harmful contaminants, especially carbon monoxides (CO) and hydrocarbons (HC), contained in the exhaust gas emitted from the engine are increased.